Method and apparatus for providing the casings of electrical apparatus with inert atmospheres



Oct. 11, 1932. T; T. GREENWOOD METHOD AND APPARATUS FOR PROVIDING THECASINGS OF ELECTRICAL APPARATUS WITH INERT ATMOSIHERES' Filed Dec 1 19262 Sheets-Sheet l Oct. 11-, 1932. T. T. GREENWOOD 1,881,510

METHOD AND APPARATUS FOR PROVIDING THE CASINGS OF ELECTRICAL APPARATUSWITH INERT ATMOSPHERES Filed Dec. 1, 1926 2 Sheets-Sheet 2 lza V 70 Anil ' mnon AND urann'rus casings.

Patented Oct. 1 1, 1932.

PATENT OFFICE TALMA T. GREENWOOD, OF EAST TEMPLETON, MASSACHUSETTS,ASSIGNOR TO CONDIT- ELECTRICAL MANUFACTURING CORPORATION, OF SOUTHBOSTON, MASSACHUSETTS,

A CORPORATION OF MASSACHUSETTS FOR PROVIDING THE CASINGS OI ELECTRICALAPPARATUS WITH INERT ATMOSPHERES v Application filed December 1, 1926.Serial No. 152,047.

. 5 oil and the gases and vapors of the oil, and

for preventing fires and explosions in such Electric switches andtransformers, for in stance, are contained in casings and immersed inoil or other equivalent liquid for the pur- J so pose of providing ahigh quality of insulation between conductors at different potentialsandalso for the purpose of rapidly extinguishing the circuit-interruptingarc of an electric switch, and an are which may sometimesoccur under theoil in a transformer.

When the contact members of an oil-immersed electric switchare separatedunder load,-large amounts of oil gases and vapors may be generated bythe circuit-interrupting are.

-This also is the case when an arc occurs under oil in a transformercasing. It is common practice to provide switches and transformers withgas expansion spaces above the oil into which the oil gases and vaporscan expand, when formed, whereby to keep down the internal pressure ofthe casing. Ordinarily air is present in the gas expansion space, eitherentering the casing through leaks in the casing joints or throughespecially provided vent passages that are employed to permit the casingto breathe under variations of the volumes of the elastic fluid andliquid contents thereof under temperature and barometric variations.

\Vhen oi-l "gases and vapors and air are present within the enclosingcasing in suitable proportions, the mixture is combustible and willexplod'e'when ignited due to heat of the arc, a static discharge orother means,

and may seriously damage the casing and apparatus. The insulatin oil orother liquid,

7 also, commonly is slow y auto oxidizable in usefulness of'the liquid.

the presence of the oxygen of the air and thickens or-sludges, therebyimpairing the To remedy or avoid the aforesaid fiiculties it has beenproposed to maintain an inert, or more particularly, a substantiallyoxygenfree atmosphere within the casing and above the oil by the use ofa material which reacts chemically with the oxygen of the air to removeit from the gaseous atmosphere with-.

in, the casing. The materials commonly sug-' gested have beenphosphorus, the alkali metals and the like wherein the oxygen and thematerial united'to form an oxide of the material. In all cases the oxidehas been apermanent oxide and the material, after having been oxidized,has been unfit for further service and must be replaced by freshmaterial. The materials heretofore proposedhave been fairly expensive,and charges thereof must be frequently removed so that the yearly costof maintenanceof an inert atmosphere by the use of such-materials isrelatively great. Furthermore, if the charge is not removed when orbefore it is spent, the

which can be re-activated-when its oxygen.

absorbing or combining ability is temporarily exhausted, whereby greatlyto reduce the expense of maintaining the inert atmosphere.

A further object of the inventionis the provision of an enclosedoil-immersed electrical apparatus and a temporary container for theoxygen content of the air within the apparatus enclosure, in whichcontainer the oxygen is temporarily retained and is isolated from theatmosphere of the casing and from which container the oxygen can beremoved to condition the container for continued service.

- Ayet further object isthe provision of means automatically-operativeto remove the oxygencontentof an enclosing casing and to discharge theoxygen externally of said case mg.

A further object is generally to improve .the construction and operationof electrical apparatus andthe production of inert atmospheres therefor.v

Fig. 1 is a side elevation of an electric switch embodying theinvention, the switch being shown in section.

' Fig. 2 is an enlarged sectional elevation of the de-oxygenatingapparatus embodying the.

invention.

Fig. 3 is an end-view of the apparatus of Fig. 1.

Fig. 4 is a diagrammatic view illustratingthe circuit connections foreffecting the automatic operation of the-apparatus.

Fig. 5 is a modified form of the de-oxygen ating apparatus.

The electrical apparatus here shown as associated with the invention,comprises an electric switch having the enclosing casing 10 adapted tocontain a' body of oil in which the fixed switch members 12 and movableswitch member 14 are immersed. The casing is provided with a cover 16through which the insulated switch terminals 18 are extend-;

ed. The casing is adapted to contain a gas expansion space 20above thebody of the oil. In accordance with this invention, the gas expansionspace is adapted to contain an inert atmosphere which is not combustiblewith the gases and oil or the equivalent liquid or with the gases andvapors thereof or with air. To

this end, I provide means to remove the oxygen from the gaseousatmosphere within the casing and also to remove the oxygentrom.

air entering the casing whereby to maintain the expansion space filledmainly with nitrogenfor with an atmosphere having such a low content ofoxygen that it is non-combustible. In carrying out my invention, I pro--suitably high temperature, as to a dark red heat. When heated to ahigher temperature,

.or subjectedto a reduced pressure, or both.

the barium dioxide gives up its oxygen and is Ire-converted to bariumoxide. I have herein utilized this principle of barium oxide to maintainan inert atmosphere within the casing of an electrical apparatus.

- Fig. 5 shows a simple form of the invention wherein a charge 22 ofbarium oxide is disposed within a suitable container 24, the open top ofwhich is closed by the removable cover 26. Said container is providedwith an upper laterally-extended neck 28 adapted to be se-' curedremovably to the side wall of the casing 10 of the electrical apparatusand having a passage 30 therein aligned with an opening 32 in the sidewall of said casing. The container 24 is also provided with alowerlaterally-extended neck 34 having a passage 36 therein which is alignedwith a lower opening 38 in said casing 10. Said container 24 is alsoprovided with a passa e 40 which is adapted to communicate with t eatmosphere. The charge of oxygen-removing material is supported upon aperforated wall or screen 42 located above said passages 36 and a wall'44 disposed immediately beneath said screen 42 serves to isolate saidtwo passages.

An electric heating coil 46 is disposed in said body of oxygen-removingmaterial and is adapted to heat said'material to a suitable temperature.As thus arranged, the heat of said coil 46'serves to set up by thermalaction a circulation of the atmosphere within said casing 10 through thelower passage 36 and upwardly through the porous mass of oxygen-removingmaterial 22 and thence through the upper passage 28 back into thecasing. In itsv passage through the material 22, the oxygen of thegaseous atmosphere within the casing 10 is abstracted so that theremaining atmosphere consists largely of nitrogen."

The casing 10 is adapted to breathe through the opening 40 upon changesof temperature so that some of the inert gas may escape to theatmosphere upon a rise of temperature of the contents of the casing.When the pressure drops within the casing,

" however, air is drawnin through the pas-- sage 40 and as it passesupwardly throu h the material 22, the oxygen thereof is a stracted sothat the gas that passes into the casing 10 is practically free from'itsoxygen content," or will be shortly subsergiently rendered so by rapidcirculation t oxygen-removing material. The preferred form of theinvention is illustrated in Figs. 2, 3 and 4 wherein means are providednot only to absorb the oxygen but subsequently to discharge theabstracted oxygen into the atmos-- 'phere. As shown in these figures,the

oxygen-removing material is enclosed within a cylindrical container 50,the open top of which is provided with a removable cover 52 rough the eand the open bottom of which is provided with a removable cover 54.

Said container is secured removably to the side wall of the'casin'g 10and is provided with anupper passage 56 which is in register withthe-upper opening 32 in the "side wall of said casing. Said container isalso provided with a. lower passage 58 which is in register withthelower opening 38 of said casing.

Said container is also provided with a second passage 60 in the upperend thereof which is adapted to communicate with the atmosphere. 'Saidpassages 60 and 56 are adapted to be opened and closed alternately bymeans of valve members 62 and 64 respectively.

Said valve members are carried upon a rod 66 which is connected witha-plunger or armature 68 at one end. Said plunger is.

- 60. A spring 72 serves to urge said plunger and the valve' in theopposite direction whereby normally to maintain said valve 64 open andsaid passage 60 closed.

The porous mass 74 of oxygen-removing material, as barium oxide, iscontained within a cylindrical basket 7 6 which is freely movable in-avertical direction in said container 50 and is adapted to be apractically gas tight fit therein so that said basket serves as a sealto prevent direct communication between said lower passage 58 and saidupper passage 56. Said basket is provided with a plurality ofperipherally-disposed perforations or openings 78 in its side wall andnear the bottom thereof through which the gas in said passage 58 maypass into the interior of said basket and thence upwardly through thematerial therein. Said basket is provided with a foraminous bottom wall80 which is 2 adapted to support the material. The bottom cover 54 isprovided with a passage 82 therein which is adapted to communicate withthe atmosphere and said passage constitutes a breather passage oropening.

Y An electric heating coil having the two electrically-connected heatingsections 84 and 86 is disposed within said basket and is adapted 'toheat thematerial therein. The terminals 88 and 90 of said sections areflexible and are brought out through a suitable terminal block 92. Athird flexible terminal 94 is also brought out from the junction betweensaid sections 84 and 86 to said terminal block 92. Said basket 76 issupported upon a sensitive compression spring 96 which is adapted topermit thebasket to move within said container in response to changes inweight of the oxygen-removing material therein contained. Said basket isprovided with a stem 45 98 which is extended freely through said bottomcover 54 and into a switch casing 100 carried by said bottom. Said stemis operatively connected with a quiok-acting switch 102 of any usual orsuitable construction, which switch is so arranged that it closes whenthe basket has been moved downwardly a prede termined distance; and saidswitch is adapted to open when said basket is moved upwardly apredetermined distance. The normal disposition of the parts isillustrated in Fig. 2 wherein the oxygen-removing material is in freecommunieation with the interior of the switch casing and also with theatmosphere through the opening 82. Both. sections 84 5 and 86 of theheater coil are adapted to be energized so that the body of material 74is maintained at a suitable temperature to be active and to absorb orcombine with the oxygen of tlfe gaseous contents of the casing 10 andalso to absorb or combine with the oxygen of the air that may enter thecontainer 50 through the opening 82 on its way to the interior of thecasing. As the material, as barium oxide, absorbs oxygen and therebybecomes gradually converted into barium dioxide it increases in weightso that the basket 76 gradually descends within the con tainer 50. d

When the amount of absorbed or combined oxygen is sufficiently great,the basket is moved into such a position that it is caused to operatethe switch 102 and close the switch circuit.

'70. The section 84 of the heating coil thereby receives moreenerg-y andso operates to heat the barium oxide to a higher temperature, thusdriving off the absorbed or COID- bined oxygen and discharging it to theatmos phere through the passage 60. As the barium dioxide loses oxygenit decreases in weight so that the basket 76 rises within the container50. When suiiicient oxygen has been liberated, as when a largeproportion of the barium dioxide has been re-converted into bariumoxide, the basket 76 is adapted to move upwardly a suiiicient distanceto effect the opening of the switch 102. The solenoid is thus cut out ofthe circuit and the spring 7 2 effects the closing of the passage 60 andthe opening of the passage 56 so that the normal or operative conditionof the de-oxygenating apparatus is restored. Both sections of the heatercoil are thus placed in service and the barium oxide cools down to thattemperature at which it is active in absorbing or combining withtheoxygen of the gas in contact therewith.

As thus arranged, a single charge of gas removing material serves indefinitely to maintain an inert gas within the casing 10 of theelectricalapparatus. The material serves as a temporary container forthe oxygen and is automatically caused to abstract the oxygen from theinterior of the casing 10 and to liberate it externally of the casing.

For certain purposes the barium oxide may be replaced by some othermaterial, as char coal, for instance, which has the power to absorb oxen in lar er uantities than other The connections of the switch cir-'cuit are illustrated in Fig. 4 and are such that fied without departingfrom the spirit of the invention.

I claim: 1. The method of providing an inert atmosphere for the casingof-an electrical apparatus which consists in placing barium oxide incommunication with the interior of the casing and activating "the bariumoxide to cause it to combine with the oxygen in the casing andsubsequently isolating the barium oxide from circulatory communicationwith the atmosphere of the casing, subjecting the bar ium oxide to suchconditions as to cause of the casing when the weight of the barium oxidehas increased materially due to its increased oxygen content andsubjecting the barium oxide to such conditions as to cause it toliberate the'combined oxygen free from intermixture with the inertatmosphere of the casing, and subsequently replacing. the

I oxygen-free barium oxide in communication with the atmos here of thecasing.

3QThe combination with the casing of an 3 electrical apparatus, of atemporary contain-1 er for the oxygen content'of the atmosphere 1 ofsaid casing comprising a body of barium oxide and automaticallyoperative means governed by the oxygen content of said barium oxide toplace said barium oxide body alternately in and out of fluid circulatorycommunication with'the casing-atmosphere, and means to subject saidbarium oxide body to varying conditions when in and out-of communicationwith the casing atmosphere.

, 4. The combination of the casing of an electrical apparatus, and meansto provide said casing with an inert atmosphere comprising atemporarycontainer for the oxygen content of the casing-atmosphere, and meansgoverned bythe amount of abstracted oxygen in said container tocondition said container to abstract the oxygen content of thecasing-atmosphere and also to liberate the abstracted oxygen free fromthe inert vatmosphere of said casing. j

5. The combination" of the casing of an electrical apparatus, and meansto provide" 0 v and-also to liberate the abstracted oxygen said casingwithan'ine'rtatmosphere com prising a temporary container for the oxygencontent of the casing-atmosphere, and automatically operative: meansgoverned by the amount of abstracted oxygen in said-com tainer tocondition said container to abstract the oxygen content of thecasing-atmosphere freefrom the inertatmosphere of'said casing, saidtemporary container including a body of barium oxide.

6. The combination of the casing of an terior of the casing, and meansto heat said body toone temperature when in communication-with theinterior of the casing to cause said body to absorb oxygen from thecasing atmosphere and to another temperature when out of communicationwith the interior of the casing to cause it to give up the absorbedoxygen.

7. The combination of the casing of an electricalapparatus, and means toprovide said casing with an inert atmosphere, said means including anoxygen-abstracting .body, means automatically operative in response tothe amount ofoxygen in said body to place said body into and also out offluid circulatory communication with the interior of the casing, andmeans to heat said body .to one temperature when in communication withthe interior of the casing and to' another temperature when out ofcommunication with the interior of the casing.

8. The combination of the casing of an electrical apparatus, and meansto provide said casing with an inert atmosphere, said means comprising abody of barium oxide, means to place said body into and also out offluid circulatory communication with the-interior of the casing, andmeans to heat said body to one temperature when in communication withthe interior of the casing and to another temperature when out ofcommunication with the interior of the casing, both the aforesaid meansfurther characterized by being operable in response to variations inweight of said body.

9. The combination ofthe casing of electrical apparatus and means toprovide said casing with an inert atmosphere comprising means to removethe oxygen content of said casing and automatically-operative meansgoverned by the amount of removed oxygen arranged to govern theoperation of'said I oxygen removin means. a

10, The combination of the casing of an electrical apparatus,-a-nd ade-oxygenating apparatus associated therewith havingautomatically-operative means governed by the amount of oxygenabstracted alternately to place said apparatus infiuid circulatorycommunication with the interior of said casing and with theatmosphere-outside of said case ing. a 11. De-oxygenat1ng apparatuscomprising a container for a mass of oxygen absorbing material, saidcontainer having a. pair of gas passages and automaticallyoperativemeans governed by the amountof absorbed oxygen to open and close saidpassages alternately.-

1'2. De-oxygenating apparatus comprising a container having a pair ofgas passages, a

basket for the absorbing material movably disposed within said containerand adapted to assume a position therein proportionate to the oxygencontent of the oxygen absorbing material, and means controlled by saidbasket to open-and close said passages alternately.

13. De-oxygenating apparatus comprising a container, a basket forabsorbing material movably disposed therein and adapted to assume aposition proportionate to the oxygen content of the absorbin material,an electric heater element dispose to heat the contents of said basket,and means governed by the position of said basket within said containerto vary the heating efiect of said heating element.

'14. De-oxygenatingapparatus comprising a container having a passage foroxygen-free as and a passage for oxygen-laden gas,.a basket for oxygenabsorbing material movably disposed Within said container and adapted toassume a position therein governed by the oxygen content of the oxygenabsorbing material, a heating element disposed to heat the contents ofthe basket, and means governed by the position of said basket with insaid container arranged to open and close said passages alternately andalso to vary the heating effect of said heating element.

In testimony whereof, I have signed my name to this specification.

TALMA T. GREENWOOD.

